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M HE time was when mankind, igno

I rant of the laws of evaporation and condensation, looked to Heaven above for their water, and piously at tributed to their gods the direct dispensations of flood and drought.

They did not suspect that the pitiless flood, on wings of gloom, had, yesterday, murmured in their lakes and brooks; that the snow, this morning so pure, so gentle, so lovingly covering away earth's unsightliness, closed, last night, over a lonely ship and washed the light from despairing eyes.

The science of 1868, however, regards the evaporation and the precipitation of Fater over the whole earth's surface as equal, evaporation being in great excess over precipitation upon the ocean only, while precipitation is excessive upon mountain ranges and toward the poles.

A certain ingenious friend of ours recently threw out the startling suggestion that water is, at times, formed suddenly and in vast quantities by a direct combination of its elements in some un known and unaccountable manner; and pointed us, in proof, to water-spouts and those sudden avalanches of water which are known to inundate mountain defiles without warning, sweeping every thing before them in demoniac fury such, perhaps, as that which has recently devastated Switzerland, and which are aot uncommon in the tropics. We were not convinced, although our friend in stanced and described such a torrent, which he had himself witnessed in the Rocky Mountains, while the air was perfectly calm and clear, and was positive in his statement that there was not, nor had there been, for days, any storm either near or remote.

It may not be impossible-- in contravention of the old aphorism that no matter has been added to the earth since its creation that once or twice in a generation a cosmical or cometary mass of water, or the elements thereof, should be discharged upon us, coming, in very truth, from the stars. We do not see a greater absurdity in accepting the occasional advent of such a meteorite than of the nickeliferous iron stones which do often fall to the earth. The anxious watchers of the 14th of November star-showers may possibly some time secure a douche bath visitation to cool off their ardor, undistinguishable from an ordinary rain storm, which yet may be as truly superterrestrial in origin as those wonderful iron stones which descend to us through so fiery a baptism.

Our inquiry, however, “Where does the water come from?" pertains to a limited portion of the earth's surface. In its discussion, we propose to admit into our consideration only such deductive reasoning as the present status of knowledge warrants.

Generally, over large areas, the amount of evaporation and the discharge by springs, lakes and rivers to the sea are completely measured by the rain-fall of the region; but over limited areas this law does not always obtain, as is assuredly the case with those gardens in the African deserts, called oases. The waters of these springy spots, which bring light, life and beauty into the very heart of Sahara, come from distant and hap. pier regions.

The existence in the desert of a considerable underflow of water was demonstrated during the recent invasion of Abyssinia by the English, when Artesian wells, now proving to be the nuclei of other cases, were sunk along the projected line of march. But for this happy expedient, it is said that it would have been impossible for the British army successfully to invade the country.

Most large rivers have their sources in mountain regions, where the amount of rain-fall is very considerable, owing to the condensing power of the cool summits of mountains upon all aqueous vapor which may be brought in contact therewith, the waters from which de. scend with too great rapidity to the plains below to be greatly diminished by evaporation. But there is a certain table-land, most of it within the bound aries of the United States, which elimi. nates more water than any equal por tion of the earth's surface not characterized by a great chain of mountains.

Let the reader cast his eyes over the map of North America, and note a certain section of country, embracing nearly the whole of Minnesota, a portion of the Territory of Dakota, western Wisconsin, a part of Michigan, and a small portion of British America bor. dering Lake Superior.

He cannot fail to be struck with the fact that this country, with an area of about one hundred and seventy thousand square miles, gives origin to Lake Superior, the first and grandest of our great North-American chain of lakes; the Mississippi, one of the largest riv. ers of the globe, flowing to the South; the Red River of the North, whose waters find their way at last through Lake Winnepeg to Hudson's Bay; and two very considerable rivers, the Big Sioux and the St. Jacques, which flow into the Missouri.

This region we would indicate by a line drawn from the western extremity of the State of Michigan on Lake Su perior to the foot of Lake Pepin on the Mississippi; thence westwardly, across Minnesota, to the Coteau des Prairies, or the divide between the headwaters of

the St. Peter's river and the Big Sioux; then northwestwardly, along the divide between the tributaries of the Missouri and the Red River of the North, to the twenty-third degree of longitude west from Washington, and the boundary line of the United States and British America; thence eastward, following the boundary line to the northern shore of Lake Superior. The area included is about equal to twice that of the State of Minnesota. This region is certainly the greatest fresh - water ooze in the world. The portion of Minnesota and western Wisconsin which we have indicated, in particular, received from Nicolet the somewhat fanciful name of “Undine Region," suggested by the great number of lakes therein. According to Schoolcraft and others, there are over ten thousand within the limits of Minnesota alone.

Many of these lakes are strung together, forming an almost labyrinthian maze. With but little portage, nearly the whole area above mentioned can be circumnavigated by boats of moderate size.

The description given by Sir I. Richardson, in his narrative of an overland expedition in search of Sir John Franklin, of the “ridge,” or divide, between the waters of Lake Superior and of Lake Winnepeg, would answer for much of the Minnesota country : “ The surface of that tract is characterized by rounded and sometimes rugged knolls of granite, rising abruptly from lakes and swamps, but only to small hights, above the general level. The term ridge is used with reference to its being a hight separating two depressions, but its summit is a marshy plateau of some extent, across which narrow winding lakes afford a canoe navigation in a variety of directions." The State of Minnesota has certainly more lakes gemming its bosom than any other equal portion of the earth's surface of which we have any account,

This table-land, throughout its extent, boring downward, until a more or less unlike most heavily-watered districts, is perfect water-shed is reached, i. e., a characterized by a remarkable uniform. rock which permits little or no water ity of elevation. It is only about four. to percolate through it. It is necessary teen hundred feet above the sea. The that this rock or water-shed should come highest ridges or elevations of the coun- to the surface in some elevated region, try are the Hauteur des Terres and the as for example, in a chain of mounCoteau des Prairies, the former being tains. In such localities, the surfacethe appellation of the low ridge of drift water received from the atmosphere accumulation dividing the basin of Lake comes in contact with this water-shed, Superior from the headwaters of the . and follows the stratum along its dip, Mississippi river, with an elevation at often to a great distance. If, then, we its highest observed point of sixteen penetrate by boring to this stratum, hundred and eighty feet above the sea, although at a point hundreds of miles and only one hundred and thirty feet from its mountain outcrop, the water from above Itasca lake, — the beautiful sheet the interior gushes up, and generally in which the Mississippi has its origin with an astonishing force and volume,

This moderate elevation of sixteen hun. and often from a great depth. The dred and eighty feet, as determined by continental water-shed with us is unNicolet, is the more surprising, when we doubtedly the igneous and metamorphic consider that it is the highest conti- rocks underlying the true sedementary Dental elevation between the Gulf of formations. The Potsdam sandstone Mexico and the northern seas, and is and calciferous sand-rock, above, furdistant from the mouth of the Missis. nish easily worn veins, reservoirs or sippi more than three thousand miles. passages for the water.

The “ Coteau des Prairies," the pe. The formations of which we speak culiar ridge which divides the valley of find a full development and exposure in the St. Peters or Minnesota river from the Rocky Mountains, and do not again that of the Missouri, has an elevation of revisit the surface in the interval until only nineteen hundred feet above the sea. we reach Minnesota, where, at a moder

The moderately elevated plateau of ate elevation above the sea, the subterMinnesota, discharging its waters to the ranean waters must experience the full four quarters of the globe, is a wonder force of that wonderful hydraulic power, ful mesh or net-work of lakes, and the which we see illustrated in Artesian fountain head of so many mighty waters, wells, and be discharged over the surand yet the precipitation of moisture face in the greatest profusion. Such is from the atmosphere, in the shape of our theory. rain and snow, is not great, indeed is far We were led to indulge in the foregobelow the average in the Eastern, Mid- ing conjectures, many years ago, while dle, Western and Southern States. living in Minnesota, and at a time when

We are, we think, prepared to show there had been no careful examinations with an approximation to certainty, that of the aqueous discharge from Lake a portion of the water discharged from Superior through Sault St. Marie or of this region is of subterranean origin, the Mississippi. coming probably from a great distance, Quite recently the United States Enurged by some great hydraulic power, gineer Corps, under the superintendence even from the Rocky Mountains. of General W.F. Reynolds and Assistant

There are few, perhaps, who do not D. F. Henry, have made several careful understand the principle of the Artesian water sections of the Sault St. Marie, Well. It is usually constructed by the St. Clair river, and Niagara. The Mississippi has also been carefully Lake Superior region it is three inches. gauged, under the direction of General These averages are taken from BlodHumphreys of the Engineer Corps, in get's tables in his valuable work upon view of new ship-canals in process of the Climatology of North America, and construction at Keokuk, Iowa, and at are founded upon careful observations Rock Island, under the enlightened continued over a period of more than superintendence of General I. H. Wilson thirty years, at various military posts. of the Engineer Corps.

The above small precipitation for the The general dryness of the atmos- winter months affords a striking contrast phere in Minnesota and the great aver for the same period with the average age heat of the summer months in that precipitation over the Atlantic States, country, added to the remarkable level which is from ten to thirteen inches. uniformity of its surface, it being char.

Notwithstanding the small amount of acterized by nothing in the remotest

winter precipitation in the country we degree resembling mountains or consid

have been considering, and the addi. erable elevations, such as distinguished

tional fact that the severity of the cold most regions where great water-courses

during the winter months precludes the take their rise — impressed us with a

à possibility of any considerable portion strong conviction of error in ascribing of the snow or water of precipitation all the water emanating from this region finding its way to the Mississippi or to to immediate atmospheric influences.

Lake Superior. Yet the Mississippi and The general absence of those irregu

the Sault St. Marie hold their volume of larities of surface which insure the water in the interim very remarkably, rapid drainage of a country, and the or rather, the decline of water stage full scope given to surface evaporation during the winter months is not unusual by the retention of the water precipi. as compared with most rivers in the tated upon its area, as rain or snow, United States. added an intensity to our convictions Another remarkable peculiarity which only to be hightened by the knowledge has not escaped popular attention in Minof the physical fact that the immense nesota is this : A very large proportion area occupied throughout this country of the snow that falls is evaporated as by lakes and swamps must perforce snow from the surface, so that there is yield up, by continual evaporation from no particular rise of the river on their surface through the year, a very the breaking up of winter. Durgreat excess over precipitation.

ing the advance of winter we have We extract from the Surveyor Gene- repeatedly heard individuals remark, ral's Report : Total area of the State of that the snows over the surface of the Minnesota, 51,479,000 acres, and 32, country in Minnesota had almost every000,000 acres arable land, leaving for where disappeared, although there had lakes and swamps 19,479,000 acres, or not been a single thaw during the winter. considerably over one-third its whole It is a popular notion, in which some me. surface.

teorologists have indulged, that the evapA striking peculiarity of the climate, oration is very inconsiderable at or below during the winter months, over this thirty-two degrees Fahrenheit, or rather whole region, is also very suggestive of during the winter. Any house-wife, the truthfulness of our views. The however, could instruct us better, with average amount of precipitation in the her oft-repeated observation, that her form of rain and snow for the three clothes “are freezing dry," so that her winter months, in Minnesota, is two weekly washing and drying need not be inches, and over west Wisconsin and the interrupted by any possible intensity of

cold. The real fact is, that evaporation, thirty inches, the observed annual rainor the drying process, goes on at all fall for this region—we have seven known temperatures.

inches as the annual excess of precipi. The great table-land which we have tation over evaporation. This will give been considering varies, as we have for 70,000 square miles an annual yield said, but little in elevation, its lakes and of 40,833 square miles of water, one streams being from fourteen hundred to foot in depth. sixteen hundred feet above the sea. The lake, being continuously exposed The lowness of the divide between the to evaporation, loses much more water head-waters of the Minnesota or St. thereby than is received from the rainPeters river and the Red River of the fall upon its surface. The annual evapNorth is evidenced in the fact that with oration from an exposed reservoir of almost no portage boats can pass at all water protected from the rain, has been seasons between the sources of the two found, in the experiments of Dr. Holrivers. We have conversed with voy yoke, continued over a series of years, at ageurs who stated that they had often Salem, Mass., to average fifty-six inches. floated from the lake-like expanse at Salem, however, has an average annual the head of St. Peters into Lake Trav. temperature considerably above that of erse, the head of the other.

Lake Superior. We will, accordingly, At the risk of some tediousness, we place the average annual evaporation will now introduce our calculations con- at fifty inches-the amount observed at cerning the amount of precipitation of Syracuse, N. Y., where the annual averwater from the atmosphere, and the age temperature is a little lower than at amount eliminated by evaporation and Fort Snelling, Minnesota. This gives discharge for the greater portion of the an excess of twenty inches per annum areas we have been considering.

of evaporation over precipitation. In Lake Superior, which drains a The area of Lake Superior is 32,000 very limited area, and whose aqueous square miles; hence, 53,333 square discharge through the Sault St. Marie miles of water one foot deep is the has been, of late, carefully estimated, annual excess of evaporation for the we find no very complicated problem lake. The discharge of water at Sault in determining the ratio of evaporation St. Marie is 90,900 cubic feet per secand discharge to the annual precipita. ond, which is 90,740 square miles of tion it receives. The land area drained water one foot deep per annum. To by the lake, excluding its own area, is this, add 53,333 square miles, the about 70,000 square miles. The aver- amount lost by evaporation from the age annual rain-fall over this region is lake surface, and the result is 144,573 thirty inches, according to Blodget's square miles one foot deep, as the total Rain Chart and the Meteorological Ta- discharged and evaporated from Lake bles. The annual average evaporation Superior per annum. If we now deduct over the general land surface in Eng. 40,833 square miles of water one foot land is estimated at twenty-three inches, deep- the excess of precipitation for which we will take as our standard in the land area drained by the lake -we the Lake Superior region, although it have 140,500 square miles of water one is well known that, owing to the great foot deep, which must be received from natural dampness of the air, in Eng. subterranean sources. Undoubtedly, land, the evaporation is much less than should this underground supply be cut anywhere in the United States. By off from Lake Superior, the lake would deducting the above amount of annual be drained by evaporation alone. evaporation - twenty-three inches from We are positive that we underesti

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